German patent application DE 10 2006 041 633 A1 discloses a pump with a housing formed from two intersecting cylindrical sections, wherein inlet and outlet openings are provided at mutually opposite sides and there is disposed, in each cylindrical section, a rotor rotatable about the central longitudinal axis thereof. The larger transverse axes of the rotors lie each time approximately normal to one another in at least one movement phase, wherein the rotors roll in a sealing manner against one another and against the housing interior wall, and the surface lines of each rotor proceeding from the point of intersection of the large transverse axes run in mutually opposite directions inclined to the respective central longitudinal axis. Each rotor comprises two approximately lobe-shaped sections, which are connected to one another at their narrower end by a constricted zone. If the large transverse axes of the two rotors lie normal to one another, the lobe-shaped shaped section of the one rotor engages in the constricted zone of the other rotor and the two rotors roll against another in a sealing manner. In each phase of the rotational movement, the two rotors form a uniformly increasing intake volume in front of the inlet opening and a uniformly diminishing outlet volume in front of the outlet opening. In order to improve the pump output and to increase the stability, provision is made such that the surface lines acting as sealing lines are constituted sinusoidal.
German utility model DE 20 2009 012 158 U1 discloses a rotary piston pump for delivering a fluid medium containing solids. The pump is provided with two rotary pistons with rotary piston vanes engaging into one another and with, in each case, a rotational axis and an outer circumference, wherein the rotational axes of the two rotary pistons are disposed spaced apart from one another and parallel to one another and the outer circumferences of the two rotary pistons partially intersect, and a housing with an inlet opening and an outlet opening as well as an inner wall and an outer wall, wherein the inner wall of the housing in each case encloses a section of the outer circumferences of the rotary pistons and wherein the rotary piston pump is constituted so as to deliver the medium in a delivery direction from the inlet opening to the outlet opening.
German utility model DE 20 2006 020 113 U1 discloses a rotary piston pump for the delivery of fluids containing solids. The problem underlying the utility model is to pump fluids containing solids in such a way that damage in the pump, in particular to the rotary pistons, is prevented. This problem is solved by at least one specially constituted ramp by means of which the inlet is optimised. This optimisation ensures that solids are conveyed at a specific point into the pump chamber of the rotary piston pump. Furthermore, a reduction in cavitation is achieved by the special design of the ramps in the inlet region and outlet region of the rotary piston pump. In order to achieve the reduction in cavitation, an increase in the so-called housing angle is absolutely essential. It is however sufficient here for only the lower housing half angle to have an angle of >90°.
German patent specification DE 94 751 A shows a positive displacement blower, in which two counter-rotating pistons are moved, with which air is compressed and fed to an outlet. The blower is provided with two special single-tooth rollers C, which each co-operate with a delivery piston in such a way that each vane of the delivery piston is allowed to pass through with a tight shut-off by roller C, as a result of which roller C rolls into the following gap and compresses the air until the vane frees the outlet to the pressure chamber.
The problem underlying the invention is to provide a rotary piston pump with which a delivery can take place as far as possible without pulsation.